Receiver assembly having a vertical tool-engaging slot for independent lock via tooling
A receiver assembly includes a receiver with a base defining a central bore for receiving the head of a bone anchor and upright arms defining a channel for receiving a rod, with the central bore having through apertures extending outwardly to outer side surfaces of the receiver and the upright arms having top surfaces, opposite front and back surfaces, vertical tool-engaging slots extending downward from the top surfaces to the through apertures for slidably receiving an insert compression tool, and horizontal tool-engaging grooves on either side of the vertical slots that extend laterally to a front or back surface of the upright arm. The assembly also includes an insert positionable within the central bore with an upward-facing outer engagement surface located within a through aperture and aligned with a vertical tool-engaging slot, and which is configured for compressive engagement by the insert compressing tool to independently lock a position of the receiver with respect to the bone anchor.
1. A receiver assembly configured for independent locking, via an insert compressing tool, to a head of a bone anchor having an anchor portion implantable into a bone of a patient, prior to securing an elongate rod to the receiver assembly and the bone anchor via a closure top, the receiver assembly comprising:
a receiver comprising a base defining a lower portion of a central bore centered about a vertical centerline axis and communicating with a bottom of the receiver through a lower opening, and a pair of upright arms extending upwardly from the base with opposed interior surfaces defining an open channel configured to receive the elongate rod, the upright arms having top surfaces defining a top of the receiver, opposite front and back surfaces, and outer side surfaces opposite the opposed interior surfaces extending downward from the top surfaces across the base to the bottom of the receiver, the central bore extending upward through the open channel to the top surfaces of the upright arms and including a discontinuous guide and advancement structure proximate the tops of the upright arms and through apertures extending outwardly through at least a portion of each upright arm to the outer side surfaces, the outer side surfaces of each upright arm further comprising:
a vertical tool-engaging slot extending downward from the top surface through to the through aperture and configured to slidably receive the insert compression tool in a direction parallel with the vertical centerline axis of the receiver, and
horizontal tool-engaging grooves located between the top surface of the upright arm and the through aperture and on either side of the vertical tool- engaging slot, each horizontal tool-engaging groove extending laterally to the front surface or the back surface of the upright arm; and
an insert configured for positioning within the central bore of the receiver, the insert having a center opening, a concave lower surface configured to engage the head of the bone anchor, and at least one upward-facing outer engagement surface positionable within one of the through apertures and aligned with one of the vertical tool-engaging slots,
wherein the at least one outer engagement surface of the insert is configured for compressive engagement by a downward-facing surface of the insert compressing tool to independently lock a position of the receiver with respect to the bone anchor.
2. The receiver assembly of claim 1 , wherein the through apertures have a substantially rectangular profile.
3. The receiver assembly of claim 1 , wherein each horizontal tool-engaging groove further comprises a downwardly-facing upper surface, an upwardly-facing lower surface, and an outwardly-facing inner surface.
4. The receiver assembly of claim 1 , wherein the at least one outer engagement surface of the insert is configured to remain uncovered by the elongate rod or by the closure top when the elongate rod is received within the open channel of the receiver and locked with the closure top.
5. The receiver assembly of claim 1 , wherein the insert is configured to be top loaded into the central bore of the receiver.
6. The receiver assembly of claim 1 , wherein the insert is configured for positioning in a first position within central bore of the receiver and then for rotation about the vertical centerline axis to a second position in which the at least one outer engagement surface becomes aligned with the vertical tool-engaging slot.
7. A pivotal bone anchor assembly comprising the receiver assembly of claim 1 and further comprising the bone anchor,
wherein the head of the bone anchor is positionable within the lower portion of the central bore and pivotally movable with respect to the receiver prior to the compressive engagement by the insert compressing tool, and
wherein the head of the bone anchor is frictionally engageable by the concave lower surface of the insert upon the compressive engagement by the insert compressing tool with the least one outer engagement surface to independently lock the position of the receiver with respect to the bone anchor.
8. The pivotal bone anchor assembly of claim 7 and further comprising the elongate rod and the closure top, wherein the closure top includes a continuous guide and advancement structure formed into an outer sidewall surface and configured to engage the discontinuous guide and advancement structure formed into the opposed interior surfaces of the upright arms of the receiver to capture the elongate rod within the open channel.
9. A method of assembling a receiver assembly configured for independent locking, via an insert compressing tool, to a head of a bone anchor having an anchor portion implantable into a bone of a patient, prior to securing an elongate rod to the receiver assembly and the bone anchor via a closure top, the method comprising:
positioning an insert within the central bore of a receiver, the insert comprising a center opening, a concave lower surface configured to engage the head of the bone anchor, and at least one upward-facing outer engagement surface, the receiver comprising a base defining a lower portion of a central bore centered about a vertical centerline axis and communicating with a bottom of the receiver through a lower opening, and a pair of upright arms extending upwardly from the base with opposed interior surfaces defining an open channel configured to receive the elongate rod, the upright arms having top surfaces defining a top of the receiver, opposite front and back surfaces, and outer side surfaces opposite the opposed interior surfaces extending downward from the top surfaces across the base to the bottom of the receiver, the central bore extending upward through the open channel to the top surfaces of the upright arms and including a discontinuous guide and advancement structure proximate the tops of the upright arms and through apertures extending outwardly through at least a portion of each upright arm to the outer side surfaces, the outer side surfaces of each upright arm further comprising:
a vertical tool-engaging slot extending downward from the top surface through to the through apertures and configured to slidably receive the insert compression tool in a direction parallel with the vertical centerline axis of the receiver; and
horizontal tool-engaging grooves located between the tops of the upright arms and the through aperture and on either side of the vertical tool-engaging slot, each horizontal tool-engaging groove extending laterally to a front surface or a back surface of the upright arm,
wherein the at least one upward-facing outer engagement surface is configured for positioning within a through aperture and aligned with a vertical tool-engaging slot and for compressive engagement by a downward-facing surface of the insert compressing tool to independently lock a position of the receiver with respect to the bone anchor.
10. The method of claim 9 , wherein positioning the insert within the central bore of the receiver further comprises top loading the insert into the central bore of the receiver through the open channel.
11. The method of claim 9 , wherein positioning the insert within the central bore of the receiver further comprises positioning the insert into a first position within the central bore and then rotating the insert about the longitudinal axis of the receiver to a second position prior to the engagement and downward compression by the insert side compressing member.